// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

// Writing to Windows Event Log requires the registry entries below to be
// present, with the following modifications:
// 1. <log_name>    should be replaced with your log name (e.g. your application
// name)
// 2. <source_name> should be replaced with the specific source name and the key
// should be duplicated for
//                  each source used in the application
//
// Since typically modifications of this kind require elevation, it's better to
// do it as a part of setup procedure. The snippet below uses mscoree.dll as the
// message file as it exists on most of the Windows systems anyway and happens
// to contain the needed resource.
//
// You can also specify a custom message file if needed.
// Please refer to Event Log functions descriptions in MSDN for more details on
// custom message files.

/*---------------------------------------------------------------------------------------

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\<log_name>]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\<log_name>\<source_name>]
"TypesSupported"=dword:00000007
"EventMessageFile"=hex(2):25,00,73,00,79,00,73,00,74,00,65,00,6d,00,72,00,6f,\
  00,6f,00,74,00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,\
  5c,00,6d,00,73,00,63,00,6f,00,72,00,65,00,65,00,2e,00,64,00,6c,00,6c,00,00,\
  00

-----------------------------------------------------------------------------------------*/

#pragma once

#include <spdlog/details/null_mutex.h>
#include <spdlog/sinks/base_sink.h>

#include <spdlog/details/windows_include.h>
#include <winbase.h>

#include <mutex>
#include <string>
#include <vector>

namespace spdlog {
namespace sinks {

namespace win_eventlog {

namespace internal {

struct local_alloc_t {
  HLOCAL hlocal_;

  SPDLOG_CONSTEXPR local_alloc_t() SPDLOG_NOEXCEPT : hlocal_(nullptr) {}

  local_alloc_t(local_alloc_t const &) = delete;
  local_alloc_t &operator=(local_alloc_t const &) = delete;

  ~local_alloc_t() SPDLOG_NOEXCEPT {
    if (hlocal_) {
      LocalFree(hlocal_);
    }
  }
};

/** Windows error */
struct win32_error : public spdlog_ex {
  /** Formats an error report line: "user-message: error-code (system message)"
   */
  static std::string format(std::string const &user_message,
                            DWORD error_code = GetLastError()) {
    std::string system_message;

    local_alloc_t format_message_result{};
    auto format_message_succeeded = ::FormatMessageA(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
            FORMAT_MESSAGE_IGNORE_INSERTS,
        nullptr, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPSTR)&format_message_result.hlocal_, 0, nullptr);

    if (format_message_succeeded && format_message_result.hlocal_) {
      system_message =
          fmt_lib::format(" ({})", (LPSTR)format_message_result.hlocal_);
    }

    return fmt_lib::format("{}: {}{}", user_message, error_code,
                           system_message);
  }

  explicit win32_error(std::string const &func_name,
                       DWORD error = GetLastError())
      : spdlog_ex(format(func_name, error)) {}
};

/** Wrapper for security identifiers (SID) on Windows */
struct sid_t {
  std::vector<char> buffer_;

public:
  sid_t() {}

  /** creates a wrapped SID copy */
  static sid_t duplicate_sid(PSID psid) {
    if (!::IsValidSid(psid)) {
      throw_spdlog_ex("sid_t::sid_t(): invalid SID received");
    }

    auto const sid_length{::GetLengthSid(psid)};

    sid_t result;
    result.buffer_.resize(sid_length);
    if (!::CopySid(sid_length, (PSID)result.as_sid(), psid)) {
      SPDLOG_THROW(win32_error("CopySid"));
    }

    return result;
  }

  /** Retrieves pointer to the internal buffer contents as SID* */
  SID *as_sid() const {
    return buffer_.empty() ? nullptr : (SID *)buffer_.data();
  }

  /** Get SID for the current user */
  static sid_t get_current_user_sid() {
    /* create and init RAII holder for process token */
    struct process_token_t {
      HANDLE token_handle_ = INVALID_HANDLE_VALUE;
      explicit process_token_t(HANDLE process) {
        if (!::OpenProcessToken(process, TOKEN_QUERY, &token_handle_)) {
          SPDLOG_THROW(win32_error("OpenProcessToken"));
        }
      }

      ~process_token_t() { ::CloseHandle(token_handle_); }

    } current_process_token(
        ::GetCurrentProcess()); // GetCurrentProcess returns pseudohandle, no
                                // leak here!

    // Get the required size, this is expected to fail with
    // ERROR_INSUFFICIENT_BUFFER and return the token size
    DWORD tusize = 0;
    if (::GetTokenInformation(current_process_token.token_handle_, TokenUser,
                              NULL, 0, &tusize)) {
      SPDLOG_THROW(win32_error("GetTokenInformation should fail"));
    }

    // get user token
    std::vector<unsigned char> buffer(static_cast<size_t>(tusize));
    if (!::GetTokenInformation(current_process_token.token_handle_, TokenUser,
                               (LPVOID)buffer.data(), tusize, &tusize)) {
      SPDLOG_THROW(win32_error("GetTokenInformation"));
    }

    // create a wrapper of the SID data as stored in the user token
    return sid_t::duplicate_sid(((TOKEN_USER *)buffer.data())->User.Sid);
  }
};

struct eventlog {
  static WORD get_event_type(details::log_msg const &msg) {
    switch (msg.level) {
    case level::trace:
    case level::debug:
      return EVENTLOG_SUCCESS;

    case level::info:
      return EVENTLOG_INFORMATION_TYPE;

    case level::warn:
      return EVENTLOG_WARN_TYPE;

    case level::err:
    case level::critical:
    case level::off:
      return EVENTLOG_ERROR_TYPE;

    default:
      return EVENTLOG_INFORMATION_TYPE;
    }
  }

  static WORD get_event_category(details::log_msg const &msg) {
    return (WORD)msg.level;
  }
};

} // namespace internal

/*
 * Windows Event Log sink
 */
template <typename Mutex> class win_eventlog_sink : public base_sink<Mutex> {
private:
  HANDLE hEventLog_{NULL};
  internal::sid_t current_user_sid_;
  std::string source_;
  DWORD event_id_;

  HANDLE event_log_handle() {
    if (!hEventLog_) {
      hEventLog_ = ::RegisterEventSourceA(nullptr, source_.c_str());
      if (!hEventLog_ || hEventLog_ == (HANDLE)ERROR_ACCESS_DENIED) {
        SPDLOG_THROW(internal::win32_error("RegisterEventSource"));
      }
    }

    return hEventLog_;
  }

protected:
  void sink_it_(const details::log_msg &msg) override {
    using namespace internal;

    bool succeeded;
    memory_buf_t formatted;
    base_sink<Mutex>::formatter_->format(msg, formatted);
    formatted.push_back('\0');

#ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
    wmemory_buf_t buf;
    details::os::utf8_to_wstrbuf(
        string_view_t(formatted.data(), formatted.size()), buf);

    LPCWSTR lp_wstr = buf.data();
    succeeded = static_cast<bool>(
        ::ReportEventW(event_log_handle(), eventlog::get_event_type(msg),
                       eventlog::get_event_category(msg), event_id_,
                       current_user_sid_.as_sid(), 1, 0, &lp_wstr, nullptr));
#else
    LPCSTR lp_str = formatted.data();
    succeeded = static_cast<bool>(
        ::ReportEventA(event_log_handle(), eventlog::get_event_type(msg),
                       eventlog::get_event_category(msg), event_id_,
                       current_user_sid_.as_sid(), 1, 0, &lp_str, nullptr));
#endif

    if (!succeeded) {
      SPDLOG_THROW(win32_error("ReportEvent"));
    }
  }

  void flush_() override {}

public:
  win_eventlog_sink(std::string const &source,
                    DWORD event_id = 1000 /* according to mscoree.dll */)
      : source_(source), event_id_(event_id) {
    try {
      current_user_sid_ = internal::sid_t::get_current_user_sid();
    } catch (...) {
      // get_current_user_sid() is unlikely to fail and if it does, we can still
      // proceed without current_user_sid but in the event log the record will
      // have no user name
    }
  }

  ~win_eventlog_sink() {
    if (hEventLog_)
      DeregisterEventSource(hEventLog_);
  }
};

} // namespace win_eventlog

using win_eventlog_sink_mt = win_eventlog::win_eventlog_sink<std::mutex>;
using win_eventlog_sink_st =
    win_eventlog::win_eventlog_sink<details::null_mutex>;

} // namespace sinks
} // namespace spdlog
